1. Field of the Invention
The invention relates to a screw of a solid-bowl screw centrifuge having a screw hub extending along a longitudinal axis and a screw helix surrounding the screw hub. The invention further relates to a use of such a screw in a solid-bowl screw centrifuge.
2. Description of the Related Art
Solid-bowl screw centrifuges are characterised by a drum with a closed or solid bowl. The drum is rotated at high speed, whereby a multiphase mixture situated in the drum can be separated into at least a heavy phase and light phase. The heavy phase is normally a solid phase which is conveyed out of the drum by means of screw. For this purpose, the screw is mounted in the drum rotatably relative thereto and has a screw helix which is arranged around a screw hub. The screw helix sweeps along the inner surface or inner lateral surface of the drum and thus conveys the material of the heavy phase to an axial end region of the drum and there in particular out of a discharge cone. The multiphase mixture to be clarified is thus situated between the inner surface of the drum and the screw hub.
In certain solid-bowl screw centrifuges, a large pond depth is desired, in particular for clarifying reasons. At the same time, however, the pond depth is limited by the diameter of the screw hub and the buoyancy and deposition effects of the mixture or the light phase to be clarified, which result there.
The diameter of the screw hub cannot be reduced to an unlimited degree, since this would negatively affect the rigidity of the screw and its stability.
The object of the invention is to provide a solid-bowl screw centrifuge having a screw, the screw hub of which can be immersed in the mixture to be separated, without disadvantages regarding the rigidity and also aforementioned buoyancy and depositions resulting.